I agree with nanaandpapa. I do take two credit cards, but they are both visa. As posted, Amex is not as accepted as Visa and Mastercard. Take your ATM and get local cash. You will need your credit cards when you sign up for the optional tours, but the charges probably won't show up until you've been back a month. Also, if you're on one of the river cruises you have to give the concierge an imprint. And then they charge purchases on the ship to that. You're given a print-out of the charges just before the trip is over so you can verify everything.
Be sure to tell your bank and your credit card companies where you'll be and when. Otherwise, the charges may not be accepted. And check with your bank to see if they have reciprocity with banks where you'll be. Sometimes, that eliminates the need for service charges.